Palladium-catalyzed Sonogashira cross-coupling of organic tellurides with alkynes

Article abstract of DOI:10.1016/j.tetlet.2011.05.134

Alkyl aryl tellurides and a tellurol ester were used as coupling partners in Pd(0)-catalyzed Sonogashira reactions. Microwave-assisted reactions of alkyl aryl tellurides with alkynes in the presence of CuI and catalytic amounts of Pd(PPh₃)₄ produced alkynyl arenes. Similarly, a tellurol ester on reaction with alkynes afforded alkynyl phenyl ketones in the presence of CuI and a catalytic amount of Pd(PPh₃)₄ at room temperature.

Full text of DOI:10.1016/j.tetlet.2011.05.134

Tetrahedron Letters 52 (2011) 4120–4122
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Palladium-catalyzed Sonogashira cross-coupling of organic tellurides
with alkynes
⇑
Shin-ichi Kawaguchi, Puneet Srivastava, Lars Engman
Department of Biochemistry and Organic Chemistry, Uppsala University, PO Box 576, 75123 Uppsala, Sweden
a r t i c l e i n f o
a b s t r a c t
Article history:
Alkyl aryl tellurides and a tellurol ester were used as coupling partners in Pd(0)-catalyzed Sonogashira
reactions. Microwave-assisted reactions of alkyl aryl tellurides with alkynes in the presence of CuI and
catalytic amounts of Pd(PPh ) produced alkynyl arenes. Similarly, a tellurol ester on reaction with
3 4
Received 30 March 2011
Revised 19 May 2011
Accepted 27 May 2011
Available online 2 June 2011
alkynes afforded alkynyl phenyl ketones in the presence of CuI and a catalytic amount of Pd(PPh
room temperature.
3 4
) at
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Alkyl aryl tellurides
Sonogashira cross-coupling
Tellurol ester
Microwaves
Organochalcogen compounds have been used extensively in
carbon–carbon bond forming reactions. Synthetically useful car-
Under the conditions of entry 4, Table 1, the coupling of various
alkyl aryl tellurides with alkynes was studied. With respect to the
product yield, ethyl phenyl telluride (2b) turned out to be a better
coupling partner than telluride 1a (Table 2, entries 1–4). Also, this
telluride was consumed completely in the reaction which simpli-
fied purification of the coupling product. Naphthalene containing
a methyltelluro group and biphenyl carrying methyltelluro groups
1
bodetelluration was observed as early as 1972 in the preparation
of biaryls from diaryl tellurides assisted by Raney nickel.2 In the
1
980s, Uemura et al. reported several transition metal catalyzed
3
cross-coupling reactions of tellurium compounds. More recently,
organotelluriums have been successfully used as coupling part-
4
5
6
7
8
0
ners in Stille, Heck, Negishi, and Suzuki reactions. Sonogashira
at the 4,4 -positions were also successfully used as coupling part-
ners (entries 5 and 6).
9
reactions have also been exploited. Much work was focused on
10
the use of readily available vinylic tellurides as coupling part-
We also studied the Sonogashira reaction of tellurol ester 4 with
1-heptyne (1a) in the presence of CuI and triethylamine as the sol-
1
1
ners, but Sonogashira reactions of aryl tellurides have received
12
13
considerably less attention. Tellurol esters have, to the best of
our knowledge, never been used in Sonogashira reactions.1
Initially, we investigated the reaction of n-butyl phenyl telluride
vent. In the absence of a Pd catalyst, the copper-assisted coupling
3
14
reaction proceeded to a small extent at room temperature (Table
3 4
3, entry 1). However, a catalytic amount (10%) of Pd(PPh ) im-
(
2a) with 1-heptyne (1a) in the presence of 1.2 equiv of CuI and a
proved the yield to 50% (entry 2). Addition of another equivalent
of CuI improved slightly the product yield, but microwave heating
and changes in the reaction temperature and time did not seem to
have much effect on the reaction. Using the conditions listed in
Table 3, entry 3, tellurol ester 4 together with phenyl acetylene,
4-tert-butylphenyl-acetylene and 1-ethynylcyclohexene, respec-
tively, afforded alkynyl phenyl ketones 5b–d in moderate yields
(Table 4, entries 2–4).
catalytic amount (10%) of tetrakis(triphenylphosphine)palladium
in refluxing triethylamine. The desired coupling product 3a was
obtained in low yield (Table 1, entry 1). Since unreacted n-butyl
phenyl telluride remained, more forcing conditions involving
microwave irradiation were investigated. This caused a slight in-
1
4
crease in the yield. When K
vents were employed, a further increase in the yield was observed
entries 3 and 4). Several other palladium catalysts as well as
NiCl (PPh were also used in the reaction (entries 4–10), but
the yields could not be improved further. The reaction time chosen
1 h) could not be shortened without a loss in product yield (en-
tries 4, 11 and 12).
2 3
CO as a base and DMF or DMSO as sol-
(
A plausible mechanism for the Sonogashira coupling of alkyl
aryl tellurides and tellurol esters with terminal alkynes is shown
in Scheme 1. First, zerovalent palladium inserts oxidatively into
an aryl tellurium or acyl tellurium bond, to generate organopalla-
dium species 6. This then undergoes transmetallation with the
copper acetylide formed from the alkyne and base in the presence
of CuI to give 7. The copper telluride species 8 which is also formed
2
3 2
)
(
⇑
Corresponding author. Tel.: +46 184713784; fax: +46 184713818.
E-mail address: lars.engman@biorg.uu.se (L. Engman).
1
5
in this reaction is likely to polymerize.
Finally, reductive
0
040-4039/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2011.05.134

S.-i. Kawaguchi et al. / Tetrahedron Letters 52 (2011) 4120–4122
4121
Table 1
Optimization of the Sonogashira reaction using n-butyl phenyl telluride
CuI (1.2 eq), catalyst (10 mol%)
conditions
n-Pentyl
n-Pentyl
a
Te n-Bu
1
2
a
3a
3
eq
1 eq, 0.3-0.6 mmol
Conditions
Et N (5 ml), reflux, 20 h
Entry
Catalyst
Yield of 3aa (%)
1
2
3
4
5
6
7
8
9
Pd(PPh
Pd(PPh
Pd(PPh
Pd(PPh
3
3
3
3
)
4
)
4
)
4
)
4
3
35
40
49
52
48
42
39
40
30
0
Et N (3 ml), 150 °C, 1 h, MW
3
K
K
K
K
K
K
K
K
K
K
2
CO
3
CO
3
CO
3
CO
3
CO
3
CO
3
CO
3
CO
3
CO
3
CO
3
(3 equiv), DMF (2 ml), 150 °C, 1 h, MW
2
2
2
2
2
2
2
2
2
(3 equiv), DMSO (2 ml), 150 °C, 1 h, MW
(3 equiv), DMSO (2 ml), 150 °C, 1 h, MW
(3 equiv), DMSO (2 ml), 150 °C, 1 h, MW
(3 equiv), DMSO (2 ml), 150 °C, 1 h, MW
(3 equiv), DMSO (2 ml), 150 °C, 1 h, MW
(3 equiv), DMSO (2 ml), 150 °C, 1 h, MW
(3 equiv), DMSO (2 ml), 150 °C, 1 h, MW
Pd(OAc)
Pd(OH)
PdCl (PPh
Pd(dba)
NiCl (PPh
None
2
2
2
3 2
)
2
2
3 2
)
1
1
1
0
1
2
Pd(PPh
Pd(PPh
3
)
)
4
(3 equiv), DMSO (2 ml), 150 °C, 5 min, MW
(3 equiv), DMSO (2 ml), 150 °C, 30 min, MW
34
37
3
4
a
Determined by 1H NMR spectroscopy.
Table 2
Sonogashira coupling of various alkyl aryl tellurides with alkynes
CuI (1.2 eq), Pd(PPh
3 4
)
(10 mol%)
C,
R
Ar Te R'
Ar
R
K CO (3 eq), DMSO (2 ml), 150
°
1
2
2
3
3
1
h, MW
3
eq
0.3-0.6 mmol
Entry
1
Alkyne
n-Pentyl
Telluride
Product
Yielda
52%
Te n-Bu
n-Pentyl
n-Pentyl
1
a
2
a
3a
3a
n-Pentyl
Te Et
b
2
3
63% (57%)
(57%)
1
a
2
Te Et
b
2
1
b
c
3b
OMe
Te Et
b
OMe
4
5
(33%)
(57%)
2
3
c
1
1
n-Pentyl
Te
Me
a
2c
n-Pentyl
3
d
n-Pentyl
Me Te
6
n-Pentyl
44%
1
a
2
d
2
2
3
e
a
Determined by 1H NMR spectroscopy (isolated yield).
Table 3
elimination occurs with product formation and regeneration of the
catalyst.
Optimization of the Sonogashira reaction using a tellurol ester
O
Organotellurium chemistry is surprisingly rich and a large vari-
ety of organotelluriums can be easily prepared. However, the num-
ber of useful reactions for transforming the carbon–tellurium bond
into useful functionality is not so impressive. The Pd-catalyzed
Sonogashira couplings of alkyl aryl tellurides and tellurol esters de-
O
Pd(PPh3)4 (10 mol%), CuI
Ph
n-Pentyl Ph C TePh
nPentyl
Et N (3 ml)
3
1
a
4
5a
3
.0 eq
0.4 mmol
1
6
Yield of 5aa (%)
scribed herein should hopefully stimulate some more activity in
this field.
Entry
Catalyst
CuI
Temp
Time (h)
1b
2
3
None
1 equiv
1 equiv
2 equiv
2 equiv
2 equiv
2 equiv
rt
rt
rt
24
24
24
24
2
21
50
58
53
54
50
Pd(PPh
Pd(PPh
Pd(PPh
Pd(PPh
Pd(PPh
3
3
3
3
3
)
)
)
)
)
4
4
4
4
4
4
5
0 °C to rt
40 °C
rt
Acknowledgments
c
6
2
Financial support from the Swedish Research Council and the
JSPS excellent young researcher overseas visit program is gratefully
acknowledged.
a
b
c
Determined by 1H NMR spectroscopy.
.5 equiv of alkyne was used.
The reaction was conducted in a microwave reactor over 2 h.
1

4
122
S.-i. Kawaguchi et al. / Tetrahedron Letters 52 (2011) 4120–4122
7. Alves, D.; Schumacher, R. F.; Brandao, R.; Nogueira, C. W.; Zeni, G. Synlett 2006,
Table 4
Sonogashira coupling of tellurol ester 4 with various alkynes
1035–1038.
8
9
.
.
(a) Kang, S.-K.; Hong, Y.-T.; Kim, D.-H.; Lee, S.-H. J. Chem. Res. 2001, 283–285;
(b) Cella, R.; Cunha, R. L. O. R.; Reis, A. E. S.; Pimenta, D. C.; Klitzke, C. F.; Stefani,
H. A. J. Org. Chem. 2006, 71, 244–250.
O
O
C
CuI (2 eq), Pd(PPh3)4 (10 mol%)
R
Ph
TePh
Ph
(a) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett. 1975, 4467–4470;
Et N (3 ml), rt, 24 h
3
1
4
R
(
b) Tohda, Y.; Sonogashira, K.; Hagihara, N. Synthesis 1977, 777–778; (c)
5
Chinchilla, R.; Nájera, C. Chem. Rev. 2007, 107, 874–922.
3
.0 eq
0.3-0.6 mmol
Alkyne
n-Pentyl
1
1
0. Zeni, G.; Ludtke, D. S.; Panatieri, R. B.; Braga, A. L. Chem. Rev. 2006, 106, 1032–
1076.
1. (a) Zeni, G.; Comasseto, J. V. Tetrahedron Lett. 1999, 40, 4619–4622; (b) Zeni, G.;
Menezes, P. H.; Moro, A. V.; Braga, A. L.; Silveira, C. C. Synlett 2001, 1473–1475;
Entry
Product
Yielda (%)
58
O
(
c) Braga, A. L.; Vargas, F.; Zeni, G.; Silveira, C. C.; de Andrade, L. H. Tetrahedron
1
a
1
Lett. 2002, 43, 4399–4402; (d) Zeni, G.; Alves, D.; Pena, J. M.; Braga, A. L.;
Stefani, H. A.; Nogueira, C. W. Org. Biomol. Chem. 2004, 2, 803–805; (e)
Raminelli, C.; Prechtl, M. H. G.; Santos, L. S.; Eberlin, M. N.; Comasseto, J. V.
Organometallics 2004, 23, 3990–3996; (f) Sha, F.; Wu, Z.; Huang, X. Synth.
Commun. 2006, 36, 2603–2612.
n-Pentyl
5
a
O
1
2. For the use of thienyl- and furyl alkyl tellurides as coupling partners, see: (a)
Zeni, G.; Nogueira, C. W.; Panatieri, R. B.; Silva, D. O.; Menezes, P. H.; Braga, A.
L.; Silveira, C. C.; Stefani, H. A.; Rocha, J. B. T. Tetrahedron Lett. 2001, 42, 7921–
2
3
4
1b
50
44
36
5
b
7
923; (b) Zeni, G.; Ludtke, D. S.; Nogueira, C. W.; Panatieri, R. B.; Braga, A. L.;
Silveira, C. C.; Stefani, H. A.; Rocha, J. B. T. Tetrahedron Lett. 2001, 42, 8927–
930.
13. Cuprous alkynylides and tellurol esters were reported to form
O
t-Bu
8
a,b-alkynones
1
d
when heated in DMF.1 Under more forcing conditions the cuprous tellurolate
thus produced added to the triple bond to form products of overall (Z)-
telluroacyl addition to the triple bond: (a) Zhao, C.-Q.; Li, J.-L.; Meng, J.-B.;
Wang, Y.-M. J. Org. Chem. 1998, 63, 4170–4171; Sonogashira coupling reactions
of selenol esters with alkynes have not been reported. An account on the
coupling of a thiol ester with an alkyne appeared only recently: (b) Mehta, V.
P.; Sharma, A.; Van der Eycken, E. Org. Lett. 2008, 10, 1147–1150.
4. In the absence of a Pd-catalyst, 1-phenyltelluro-1-heptyne (19% yield) was the
only product formed in addition to 5a after 24 h at room temperature during
which the tellurol ester was consumed completely. Running the palladium-
catalyzed and copper-assisted coupling reaction at 60 °C for 24 h resulted in a
complex mixture where 1-phenyltelluro-1-heptyne was one identifiable
product (31%) in addition to 5a (25%).
3a
5
c
t-Bu
O
1
e
5
d
1
a
Isolated yield.
1
5. (a) Davies, I.; McWhinnie, W. R.; Dance, N. S.; Jones, C. H. W. Inorg. Chim. Acta
1978, 29, L217–L220; (b) Gardner, S. A.; Trotter, P. J.; Gysling, H. J. J. Organomet.
Chem. 1981, 212, 35–42.
Pd(0)Ln
R1 Te R2
R1
R3
6. General experimental details: organotellurium compounds 2a, 2b,17 2c,18 2d,18
1
7
1
and 4a19 were synthesized according to the literature. DMSO and Et
purified by distillation before use. A Biotage Initiator 60 instrument was used
24
3
N were
R1 = Ar or PhC
O
2
0
21
22
23
for the microwave experiments. Coupling products 3a, 3c, 3d, 3e, 5a,
24
25
26
5b, 5c, and 5d are all described in the literature. Diphenylacetylene (3b)
is commercially available.
R1 PdLn
General procedure for the Sonogashira coupling of alkyl aryl tellurides. Alkyl aryl
telluride 2 (0.5 mmol) was placed in a 5 mL microwave reaction glass vial
together with CuI (0.6 mmol), Pd(PPh ) (0.05 mmol), K CO (1.5 mmol), and
3 4 2 3
DMSO (2 ml) and sealed under argon with a Teflon cap. After microwave
irradiation for 1 h at 150 °C, the crude mixture was quenched with EDTA (satd
R1 PdLn
Te R2
R3
7
6
aq; 30 mL) and extracted with CH
and evaporation, the residue was extracted with pentane (20 mL) and H
(20 mL). After separation, drying over MgSO
2
Cl
2
(50 mL ꢀ 2). After drying over MgSO
4
2
O
CuI
base
4
and evaporation, the crude
CuTe R2
Cu
R3
R3
product was purified by silica gel chromatography (eluent: pentane/EtOAc) to
give the coupling product 3.
General procedure for Sonogashira coupling of a tellurol ester. To tellurol ester 4
8
(
0.5 mmol) in a 10 mL 2-necked flask under an argon atmosphere were added
the alkyne (1.5 mmol), CuI (1.0 mmol), Pd(PPh (0.05 mmol) and Et N (2 mL).
After stirring for 24 h at room temperature, the crude mixture was quenched
with EDTA (satd aq; 30 mL) and extracted with Et
O (50 mL ꢀ 2). Drying of the
organic phase over MgSO , evaporation and silica gel chromatography of the
Scheme 1. A plausible mechanism for the Sonogashira reaction of alkyl aryl
tellurides and tellurol esters.
)
3 4
3
2
4
residue (eluent: pentane/EtOAc) yielded the coupling product 5.
7. Irgolic, K. J.; Busse, P. J.; Grigsby, R. A. J. Organomet. Chem. 1975, 88, 175–180.
8. Engman, L.; Hellberg, J. S. E. J. Organomet. Chem. 1985, 296, 357–366.
9. Gardner, S. A.; Gysling, H. J. J. Organomet. Chem. 1980, 197, 111–121.
0. Moon, J.; Jang, M.; Lee, S. J. Org. Chem. 2009, 74, 1403–1406.
References and notes
1
1
1
2
2
1
.
(a) Patai, S.; Rappoport, Z. In The Chemistry of Organic Selenium and Tellurium
Compounds; John Wiley & Sons: New York, 1985; Vol. 1,; (b) Petragnani, N;
Comasseto, J. V. Synthesis 1986, 1–30; (c) Petragnani, N.; Comasseto, J. V.
Synthesis 1991, 793–817; (d) Petragnani, N.; Comasseto, J. V. Synthesis 1991,
1. Rubin, M.; Trofimov, A.; Gevorgyan, V. J. Am. Chem. Soc. 2005, 127, 10243–
1
0249.
2. Katritzky, A. R.; Abdel-Fattah, A. A. A.; Wang, M. J. Org. Chem. 2002, 67, 7526–
529.
3. Adomeniene, O.; Adomenas, P.; Velyvis, A.; Paskoniene, R.; Goto, Y. Mol. Cryst.
Liq. Cryst. A 1995, 260, 269–272.
8
97–919; (e) Petragnani, N.; Stefani, H. A. Tetrahedron 2005, 61, 1613–1679.
2
2
2
3
.
.
Bergman, J. Tetrahedron 1972, 28, 3323–3331.
(a) Uemura, S.; Wakasugi, M.; Okano, M. J. Organomet. Chem. 1980, 194, 277–
7
2
83; (b) Uemura, S.; Fukuzawa, S. Tetrahedron Lett. 1982, 23, 1181–1184; (c)
Uemura, S.; Fukuzawa, S.; Patil, S. R. J. Organomet. Chem. 1983, 243, 9–18.
For a review of Pd-catalyzed coupling reactions of organotellurium compounds,
see: Zeni, G.; Braga, A. L.; Stefani, H. A. Acc. Chem. Res. 2003, 36, 731–738.
Kang, S.-K.; Lee, S.-W.; Ryu, H.-C. Chem. Commun. 1999, 2117–2118.
Nishibayashi, Y.; Cho, C. S.; Uemura, S. J. Organomet. Chem. 1996, 507, 197–200.
24. Wang, B.; Bonin, M.; Micouin, L. J. Org. Chem. 2005, 70, 6126–6128.
25. Liu, J.; Peng, X.; Sun, W.; Zhao, Y.; Xia, C. Org. Lett. 2008, 10, 3933–3936.
26. Chen, L.; Li, C.-J. Org. Lett. 2004, 6, 3151–3153.
4
.
5
6
.
.